Transfer and/or Breakup Modes in the ${}_{}{}^6{}_{}{}^{}He+{}_{}{}^{209}{}_{}{}^{}Bi$ Reaction near the Coulomb Barrier

Reaction products from the interaction of ${}^6\mathrm{He}$ with ${}^{209}\mathrm{Bi}$ have been measured at energies near the Coulomb barrier. A ${}^4\mathrm{He}$ group of remarkable intensity, which dominates the total reaction cross section, has been observed. The angular distribution of the group suggests that it results primarily from a direct nuclear process. It is likely that this transfer and/or breakup channel is the doorway state that accounts for the previously observed large sub-barrier fusion enhancement in this system.